Identifying stocks that are overbought or oversold can be an important part of establishing buy and sell points for stocks, exchange-traded funds, options, forex, or commodities. An oversold market is one that has fallen sharply and is expected to bounce higher. On the other hand, an overbought market has risen sharply and is possibly ripe for a decline. Though overbought and oversold charting indicators abound, some are more effective than others.
- Overbought and oversold indicators abound, but RSI and stochastics have stood the test of time.
- Relative strength index indicates overbought conditions when it moves towards 80 and oversold conditions when it falls below 30.
- While RSI is computed using average gains and losses, stochastics compares the current price to its range over a given period of time.
- RSI and stochastics are available on most charting applications, and the default setting is 14 periods, which can be days, weeks, or months.
Relative Strength Index
Two of the most common charting indicators of overbought or oversold conditions are relative strength index (RSI) and stochastics. Developed by J. Welles Wilder Jr. and introduced in the 1978 book New Concepts in Technical Trading Systems, RSI is a measurement of stock price change momentum. RSI is a range-bound oscillator, meaning that its value fluctuates between 0 and 100 depending on the underlying security performance, and is calculated based on prior periods' average gains versus losses.
When the RSI indicator approaches 100, it suggests that the average gains increasingly exceed the average losses over the established time frame. The higher the RSI, the stronger and more protracted the bullish trend. A long and aggressive downtrend, on the other hand, results in an RSI that progressively moves toward zero.
RSI levels of 80 or above are considered overbought, as this indicates an especially long run of successively higher prices. An RSI level of 30 or below is considered oversold.
As the number of trading periods used in RSI calculation increases, the indicator is considered to more accurately reflect its measure of relatively strong or weak moves. An RSI setting to use 14 days of data is more compelling than a setting of only seven days. The standard (default) on most charting applications is 14 periods, which can be measured in minutes, days, weeks, months, or even years.
While relative strength index is calculated based on average gains and losses, stochastics compares the current price level to its range over a given period of time. Stocks tend to close near their highs in an uptrend and near lows in a downtrend. Therefore, price action that moves further from these extremes toward the middle of the range is interpreted as an exhaustion of trend momentum.
A stochastic value of 100 means that prices during the current period closed at the highest price within the established time frame. A stochastic value of 80 or above is considered an indication of an overbought status, with values of 20 or lower indicating oversold status. Like RSI, the default setting for stochastics is 14 periods.
The Bottom Line
Both the relative strength index and stochastics have strengths and weaknesses, and the indicators are best used in combination with other tools designed to establish optimal buy and sell points. Lastly, there are times when a stock, commodity, or market can stay overbought or oversold for a considerable time period before a reversal. Therefore, overbought or oversold signals from RSI or stochastics can sometimes prove premature in strong trending markets.